Magnetic record indexing device

ABSTRACT

A record indexing device for a dictating machine having a sound head carriage movable along the length of a cylinder. The indexing device includes a limit switch arranged in the path of motion of said sound head carriage to be actuated by it when it is returned and a return element which acts to put the sound head carriage into its starting position. When the carriage is returned, the return element pushes the sound head carriage in its starting position and the limit switch is deactivated to set the cylinder in its start position. This enables one position, i.e., the starting position, to be determined automatically when using the machine both for recording and reproducing.

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority Kurt Guettinger Pfafihausen, Switzerland 787,082

Dec. 26, 1968 Jan. 19, 1971 Dictaphone international AG Wettingen (Aargau), Switzerland Dec. 28, 1967 Switzerland MAGNETIC RECORD INDEXING DEVICE References Cited V UNITED STATES PATENTS 2,318,628 5/1943 Proctor 274/22 2,622,001 12/ 1 952 Cooley 274/22 2,756,057 7/1956 Parkinson 274/22 Primary ExaminerHarry N. l-laroian Attorney-Curtis, Morris & Safford ABSTRACT: A record indexing device for a dictating machine having a sound head carriage movable along the length of a cylinder. The indexing device includes a limit switch arranged in the path of motion of said sound head carriage to be actuated by it when it is returned and a return element which acts to put the sound head carriage into its starting position. When the carriage is returned, the return element pushes the sound head carriage in its starting position and the limit switch is deactivated to set the cylinder in its start position. This enables one position, i.e., the starting position, to be determined automatically when using the machine both for recording and reproducing.

PNENTED JAN 1 9 I971 mwc/vwm KURT GUT TINGER 1/ ATTORNEYS MAGNETICRECORD INDEXING DEVICE This invention relates'to dictating machines which use magnetic sheets or belts as sound recording media.

More specifically this invention relates to such machines having a cylinder driven by an electric motor through a magnetic clutch in a feeding direction only, a sound'head carriage carrying a sound head for recording and reproducing sound and an operating device for setting the operating states of the machine. In such machines the sound head carriage is guided parallel to the cylinder shaft and can be moved back and forth between a stop at the front end of the cylinder and a stop at its rear end, both by hand and automatically by a feed drive and a return device.

The magnetic sheet, sometimes calleda foil, used in such I dictating machines usually has a reinforced upper edge which is place in a longitudinal slot in the cylinder. The remainder of the sheet wraps around and rests on the-cylinder surface without being secured to it other, thanby its edge secured in the slot. Because no other fastening means are provided, the cylinder may be turned in one direction, i.e., the feeding direction, only; otherwise, should the machine be rotated in the reverse-direction, the free end of the sheet would come loose from the cylinder and become damaged by contact with the machine. The feed of the soundhead carriage is achieved by a spindle couplcd'to the cylinder. Since this is so,'the coupled spindle, also, can turn in one direction only. Therefore,

. 2 Q 7 sound head carriage for disconnecting, when actuated by the sound head carriage, the return device for the sound head carriage and for connecting the magnetic clutch for the cylinder drive, and by a return element, likewise arranged at the end of the return path, which acts on the sound head carriage to move it into a starting position. This return element can be displaced to a limited extent in the feeding direction, i.e., the direction'of rotation of the cylinder, by a return cam turning with the cylinder. The return element is connected with the return cam during this displacement by a linkage whose end part proximate to the cam can be displaced into path of motion of the cam by the returning. sound head carriage immediately before it actuates the limit switch. When the linkage is engaged by the return cam, the sound head carriage, through the linkage and the return element, moves the sound "head carriage into a starting position. Also, the cylinder is since reverse rotation of the spindle is not possible, a separate device is required for automatically returning the sound head carriage.

In these foil-type dictating machines, as well as in some belttype dictating machines, the automatic return of the sound head carriage to its starting position is effected in steps by activating a control on the microphone. When the sound head carriage is returned thusly, the starting position is determined by a stop only. This being so, at best, that is, if no other defects or shortcomings are present, the starting position of the sound head carriage, and thus the start of the recording and reproduction respectively is set only generally to the first sound track. It is not set to a specific starting position on this track. Therefore, the actual starting point must be found,

both during pickup, that is, during dictation, and during the recording ofthe spoken text on the magnetic sheet in order to listen to the text again from the start.

Frequently, when working fast, the sound head carriage is often returned, for simplicitys sake, by hand, with more effort than is necessary. This places relatively great stress on the lightweight sound head carriage and,'also, over a period of time leads to deformations of the magnetic sheet so that the first sound track on the magnetic sheet gradually is displaced, making even the first track difficult to locate.

The starting point must be found also at other times in the use of such dictating machines such as when playing back the magnetic sheet on another machine for transcribing the recorded text or when the sound head carriage rebounds from the stop.

Certain measures can be taken to overcome this problem of finding the first sound track and the exact starting point turned into fixed rotary, i.e., angularly, starting position which is determined by the disengagement of the linkage and the deactuation of the limit switch after the carriage is set to its starting position.

The limit switch consists of a pair of contact springs connected into the current supply for both the return device, i.e., the return device for returning the sound head carriage to the front end of the cylinder, and the magnetic clutch. The linkage can consist of a pawl which can be rotated and displaced perpendicularly to the cylinder shaft and which has one from which acts on the pair of contact springs and which has a return element. The return element can comprise, in the simplest case, a nose, or extension having an edge extending obliquely in the feeding direction, i.e., towards, the sound head carriage to engage an edge on the sound head carriage so that when the pawl is displaced, the edge on the sound head carriage slides on the nose edge which urges the sound head carriage in its feeding direction. The edge on the sound head carriage can be the edge of an opening in a sidewall of the sound head carriage, facing the limit switch, into which the nose dips when the sound head carriage returns. The end part of the pawl near the cam can be a carrier hook which can be engaged and moved by the return cam. The return spring is preferably held in its rest position. The displacement of the pawl by the return cam which turns with the cylinder can be divided by a control into two successive phases. In the first phase, the pawl is displaced perpendicularly to the cylinder shaft until the nose is disengaged form the opening in the sound head carriage. When this happens the sound head carriage has been moved into its starting position. In the second phase the pawl is turned until the carrier hook is disengaged from the return cam and the pawl is urged back by the return spring into its rest position. When this happens the limit switch returns likewise to its rest position and the cylinder drive is stopped. The rotary, i.e., angular, starting position of the cylinder is determined by this disengagement of the switch. The movement of the pawl can be controlled by a journal secured to a support. A guide edge of the pawl slides along an edge of the journal during the displacement of the pawl.

The invention will now be described more fully in connection with the drawing in which:

thereon. The cylinder can be displaced about its axis by adjusting a lever. Also, to avoid a rebound of the sound head carriage, a permanent magnet can be provided on the stop to retain the sound head carriage in its starting position. Despite these measures, it is troublesome to have to locate the first sound track and the exact starting pointthereon.

It is the object of the invention'to provide a dictating machine where the sound head carriage and the cylinder are always brought automatically to a certain starting position after each return of the sound head carriage.

This object is achieved in accordance with the invention by a limit switch arranged at the end of the return path of the FIG. 1 is a schematic front elevational view of a foil-type dictating machine embodying the invention and having its cover removed to show details of the machine;

FIG. 2 is a top plan view of the left part of the dictating machine represented in FIG. 1;

FIG. 3 is a partial section along the line IIIIII in FIG. 2; and FIG. 4 is a diagram of the electrical circuitry for the limit switch of the machine.

In the magnetic-sheet type dictating machine represented in t the drawing, two bearing blocks 2a and 2b are mounted in a foil would come loose and be damaged by contact with the machine. The cylinder 4 is driven by an electric motor (not represented in the drawing) through a friction wheel gear and a magnetic clutch, of which only the driving wheel 6, se eu r'ed on the cylinder shaft 3, is represented in FIG. 3. The cylinder shaft 3 also carries at both its ends a hand wheel 7 with which the cylinder can be turned by hand. A guide 8 is secured parallel to the cylinder shaft in the two bearing blocks 2a and 2b. A sound head carriage 9 is slidingly mounted on this guide. A sound head 10 is mounted in the sound head carriage 9. The machine is provided with a driving spindle 11 which is rotatably mounted at both ends in the bearing blocks 2a and 2b for displacing the sound head carriage. This spindle 11 is driven by the cylinder shaft acting in cooperation with appropriate linkage, for example, cam belt 13, and cooperating pulleys or wheels 12 and 14 each respectively attached tothe cylinder shaft and the spindle. Because the magneticsheet has only its frontedge engaged in the cylinder, as mentioned above, the cylinder may only turn in one direction. Ac-

cordingly, the driving spindle for the sound head carriage which is coupled to the cylinder likewise can turn onlyin one direction, i.e., in its feeding direction. I

i In the represented embodiment, the sound head carriage 9 comprises a frame 15 which is displaceably, i.e., slidably, mounted at its upperend on the guide 8. Side parts 15a of the frame15 act as angle levers. The guide 8 extends-through the fulcrums of these levers (see FIG. 3). The short lever arms of sidelSa extend towards the front of this machine and their ends are connected by a pivot which extends parallel to the guide '8 on which a key 19 is mounted for rotation. The upper end ofthe key 19 defines a finger support, or finger piece, 21 and .theflower end a U-shaped guide part 22, whose two legs beattlightly on the lateral faces of a guide bar 23 extending in the longitudinal direction of the cylinder on the housing bottom 1. The frame 15 is tilted to the rear about the guide by pressing on the finger support 21 of the key 19. A U-shaped attachment 43 is secured on the bottom crossbar 42 of the sound head carriage frame 15 which extends behind the spindle 11. A stirrup. :16, with a straight'center part extending parallel to thespindle 1 l, is mounted at both ends for rotation in the bearing blocks 2a and 2b (see FIG. 1). The sound head carriage'guide is attached by its U-shaped part 43 to the center part of the stirrup 16 (see FIG. 3).

"The'bottom crossbar 42 of the sound head carriage frame 15 carries a carrier lever 44 mounted for rotation. This lever is only schematically shown in FIG. 3. The lever has a comb, or series ofridges, at both ends for engaging the thread of the spindle. The stirrup 16 is urged by a spring (not represented in the drawing) toward the spindle so that the tow combs of the carrier lever 44 engage the thread of the spindle. When the spindle turns, the sound head carriage is displaced in its feeding direction along the guide 8. One end of the carrier lever 44 is urged toward the spindle by a spring. The other lever end is associated with a stop so that, when the sound head carriage frame 15 is tilted about the guide 8, the comb at the stop end of the lever is disengaged from the spindle thread. When the frame is tilted further, the other comb is likewise lifted from the spindle thread. In this tilted position of the frame, the

sound head carriage is uncoupled from the spindle drive and can be moved by hand in both directions along the cylinder. Then, when the frame 15 swings back, since the fulcrum of the carrier lever is farther away from the spindle than it is when theframe 15 is in its rest position, the comb, advanced by the spring, engages the thread of the spindle in such a way that the top of a descending flank of a comb tooth strikes the top of an ascending flank of a turn of the spindle thread. When the frame is tiltedback completely into its rest position, the two flanks glide on one another and the sound head carriage is pushed back by one turn of the spindle, that is, by one sound track.

The automatic return of the sound head carriage is effected by the successive tilting of the sound head carriage frame by ineans of the stirrup 16 which is operationally connected to a suitable driving device. Such a driving device can consist, for example, as representedin the drawing, ofa magnet coil 17 (see 2) which is fed by current impulses. The magnet coil 17 surrounds an armature 18 which acts on the stirrup 16. This armature is adapted to cause the stirrup 16 tobe pulled back when the coil 17 is energized. These currentimpulses of the sound head carriage are triggered by actuating a control on the microphone. With each actuation of the return control on the microphone, the sound head carriage is pushed back by one sound track until it reaches the end of its return movement, that is, the front of the cylinder.

A limit switch to be actuatedby the sound head carriage is placed at the end of the return path of the soundhead carriage. In the represented embodiment, this limit switch comprises a pair of contact springs 45 and 46. These two contact springs 45 and 46 are arranged in series asviewed in the direction of displacement of the soundhead carriage. They are secured on the bearing block 2b shown on th'e left side in thedrawing. They are fastened, for example, attheir bottom ends by a head screw 'Electrically irisulating intermediate pieces are used between andto' each side of the lower contact ends. The upper end of the contact spring 45 next to the bearing block has a flat contact'whi'ch rests on an adjusting screw (not shown in thedrawing for the sake of clarity) in thebearing block 2b. It thus formsa fixed stop. The other contact spring 46 is bent away from the first spring'so that the contact is open in rest, position. Itsupper endon the sidefacing the fixed contact spring 45 has afcontact'point on one s'ide'and a shield, orhood, 46a of electrically insulating material on the other side I j" j,

The two contact springs d 46 are connected into the control circuit of themachine solthat, when the contacts are closed, that is, when the swi't'ch'is actuated, the magnet coil 17 is supplied with direct current so that the stirrup 16 isheld in retractedposition by the armature'18 and the sound head carriage is lifted from the driving spindle 11. Also, when the switch is actuated, the magnetic clutch of thecylin'der is engaged and the cylinder is thus coupled with, its drive. When the contacts 45 and 46 are closed. the jso nq head carriage remains in its retracted position while 'the cylinder and thus the spindle turn. i: 1 l

A return element is arranged lug on the bearing block 2b. This return element comprises a flat oblong pawl arranged with one end protruding'i nto themachineabove a cylindrical extension' 's l of the cylinder 4 andian r end pointing out from the machine between the-'pairo contact springs 45 and 46 and'the front sidepart'l'SZi-fia,that the side part on the left as viewed in F IG;'1', of the sound head carriage. This pawl 50 is mounted on the bearing block .partifor lug, 49 for rotation about a vertical axis and is held by a 52 in a rest position in which the contact springs 45 and 46 are open.

During the return of the sound head carriage 15, the side part 15a strikes the front end of the pawl and pushes it in the direction of the contact springs causing it to push spring 46 into spring 45 until they contact. The 'front end of the pawl 50 has a triangular nose or protrusion "53 "which'engages a rectangular opening 54 (see FIG. 3) in the left side'p a'rtlsa of the "sound head carriage when the carriage is pushed back, that is,

to the left (see FIG. 1), far enough.

The nose preferably has a straight sliding surface 55 extending obliquely in the direction of motion of the sound head carriage, that is, to the right as viewed in the: drawing. This nose strikes against the rear lateral edge 56 of the rectangular opening 54 in the frame part 15a. Thepawl 50 is mounted on the bearing block part 49 for displacement toward'both the spindle and cylinder shaft respectively. When the sound head carriage has been pushed all the way back, that is, to the extreme left, one end of the pawl is displaced in towards the machine. Then the sound head carriage '15 is displaced by the sliding edge 55 in feeding direction until the nose slips out of the rectangular opening 54. This displacement of the pawl 50 is effected by the cylinder 4 which turns because the contacts 45 when the soundhead carriage is pushed back and the switch 45 and 46. is closed the rear pawl arm 60 strikes against radial front edge of the plate.

When the sound head carriage is retracted, that is, when it is at the extremeleft, the carrier-hook 57 is placed in the path of motion of the return cam 58 which turns 'with the cylinder. When the cylinder turns, the return cam 58 strikes against the carrier hook 57. The pawl 50 is displaced in the direction of motion of the cylinder by the return cam 58, and the sound head carriage I5 is advanced as described above. I

When the pawl 50 is displaced, the spring 52 of the pawl is tightened. After the'pawl has been displaced for a sufficient distance, the nose 53 of the pawl becomes disengaged from the opening 54 in the side part 15a of the sound head carriage. The nose then rests with its point on the side part next to the opening 54. in this instantaneous position the carrier hook 57 still is hooked onto the return cam 58.

An oblong slot 61 is provided in the wider center part of the pawl 50. This slot is engaged by a journal 62 secured in the bearing block part 49. This journal 62 passes through the slot 61. One end of the spring 52 is secured to this journal 62 and the other end to an. eyelet 63 in a section which is bent up at the front edge of the pawl. The spring therefore, pushes the pawl 50 to the front until the journal 62 strikes against the rear end of the oblong slot 61. In this position the pawl 50 can turn about the journal 62. Since the eyelet 63 is outside of the plane normal to the cylinder shaft which intersects the journal 62, the pawl 50 is turned by the spring 52 (and also by the contact spring 46) counterclockwise until (as viewed in FIG. 2) its front arm strikes against a stop 64,whichis, for example, arranged on the bearing block part 49. This position is the rest position of the pawl.

The stop 64 and the oblong slot 61 are arranged so that when the pawl is in this rest position the carrier hook 57 is completely outside the path of motion of the return cam 58. A free rotation of the cylinder is thus enabled. Also, in this position the contacts 45 and 46 are open, the insulating, shield or ment, the pawl turns at the same time counterclockwise. The nose 53 on the front arm of the pawl dips into the opening 54 of the sound head carriage which has been pushed into its hood 46 of the elastic contact spring 46 rests against the front edge of the pawl 50, and the nose 53 of the pawl is at the point I on the frame 15a determined, i.e., defined by the opening 54 when the sound head carriage is retracted.

When the sound head carriage is pushed back, i.e., to the left, the above-described rotary movement of the pawl takes place. The fulcrum for this movement is detennined by the rear end of the oblong slot 61.

The oblong slot 61 has a rear part 65 extending perpendicu- 15a of the sound head carriage, as-described above, the journal 62 rests on the bend in the oblong slot and the carrier hook 57 still extends all the way behind the return cam 58 on the cylinder. During a further slight rotation of the cylinder, the pawl 50 is pushed further to the rear, but the oblique portion 66 of the oblong slot now slides on the journal 62 and the pawl 50 is turned counterclockwise about the point of the nose 53, which is resting on the sound head carriage, until the carrier hook 57 becomes disengaged from the return cam 58. At this moment when the return spring is tight, the pawl 50 is held neither by the sound head carriage 15 nor by the return cam 58, so that it snaps forward until the journal 62 strikes against the rear end of the oblong slot. During this forward movestarting position, and the limit switch 45 and 46 is suddenly opened. During the opening of the switch 45 and 46, the magnetic clutch 67 for the cylinder drive is disconnected and the cylinder remains in the position determined by the disengagement of the carrier hook 57. This cylinder position is its starting position.

FIG. 4 shows an example of a circuit'for the limit switch 45 'and 46.

As shown in the figure, the magnet coil 17 and the magnetic clutch 67 are supplied with a DC voltage which is indicated in the FIG. by a plus sign. The output of the magnetic clutch '67 and the magnetcoil coil 17 each lead respectively through diodes 68 and 69 to the fixed contact spring 45. The moving contact spring 46 is connected to the negative pole of the DC source. When the limit switch 45 and 46 is closed, current flows through the magnet coil 17 and the clutch 67, so that the stirrup 16 remains in the attracted position and the magnetic clutch 67 remains engaged until the limit switch 45 and 46 is opened again.-

The magnet coil and the magnetic clutch can also be operated, as mentioned above, separately by switches, i.e., a

control, provided on the microphone. These switches are likewise connected through diodes to the corresponding outputs of the magnet coil and magnetic clutch.

'During the return of the magnetic sound head carriage, whether by hand or by the control in the microphone, the cylinder preferably is uncoupled fromits drive, although this is not necessary. The sound head carriage is then merely pushed back to the stop. From this point the setting of the sound head carriage and of the cylinder to their starting positions is achieved automatically. If the cylinder was in its rest before the sound head carriage was pushed back, it is also in rest after the setting of the starting post positions, and it is possible to start with the recording of the dictation. When the machine is switched to reproduction, and the cylinder is rotating, the sound head carriage can be pushed back by hand. After the sound head carriage has been pushed back, it and the cylinder are set automatically to their starting positions. Since all this takes place with the cylinder rotating, the reproduction starts exactly at the start of the dictation without the use of any additional switches.

The foil is merely engaged, as mentioned above, with its reinforced upper edge in the oblong slot of the cylinder. For placing the foil and for removing it from the cylinder while it is rotating, the sound head carriage can be pushed back by hand. After the sound head carriage has been pushed back, it and the cylinder are set automatically to their starting positions. Since all this takes place with the cylinder rotating, the reproduction starts exactly at the start of the dictation without the use of any additional switches.

The foil is merely engaged, as mentioned above, with. its reinforced upper edge in the oblong slot of the cylinder. For placing the foil and for removing it from the cylinder an opening in the housing hood is usually provided. When the foil is removed after a recording has been made thereon, cylinder must be turned, in most cases, by hand in such a way that in such a way that the oblong slot in the cylinder is positioned beneath the inset opening. This manipulation is annoying during both the recording and during the reproduction of the text on the magnetic sheet. it is particularly annoying when several foils are used for a text. Since the starting position of the cylinder depends on the position of the return cam and the arrangement of the pawl and its carrier hook respectively, as described above, the arrangement can be such that the oblong slot of the cylinder will be positioned in the rotary starting position beneath the insert opening in the housing. Then, when a foil is replaced, it is necessary only to return the sound head carriage so that the cylinder is set in the best position for the exchange of the foil. Then the old foil can be easily removed and a new one inserted, without need to rotate the cylinder. For returning the cylinder and the sound head carriage again, it is merely necessary to briefly activate the control on the microphone several times.

When the sound head carriage is returned, it strikes against the return pawl which is held in its rest position by the return spring 52 and the contact spring 46. Because of this elastic stop, theaparts are not stressed excessively even when they are pushed back vigorously and the sound head carriage cannot recoil.

l. A dictating machine comprising, in combination, a cylinder driven in a feeding direction through a clutch, a sound head carriage with a sound head for recording and reproducing sound, said sound head carriage being adapted to iniove along a path parallel to the axis of said cylinder, a limit switch to engage said clutch with said cylinder, said switch being positioned adjacent to one end of said cylinder in the return path of movement of said sound head carriage and adapted to be actuated by said sound head carriage, means to place said sound head carriage in a starting position and to deactuate said limit switch after it has been actuated, said means including a return element arranged adjacent said one end of said cylinder and adapted to displace said sound head carriage and to be displaced by a return cam fixed to rotate with said cylinder, a linkage extending from said return element and having one end adapted to be disposed in the path of movement of said rotating return cam, said cam being adapted to contact said linkage whereby when said cam contacts said linkage said return element is moved, thusly displacing said sound head carriage to said starting position and deactuating said limit switch to set said cylinder in a starting rotary position.

2. A dictating machine as described in claim 1 having a return device operatively associated with said carriage for automaticallyreturning said sound head carriage to one end of said cylinder, a control circuit connected to said machine for setting the operating states of the machine and wherein said limit switch is used to deactivate said return device.

3. A dictating machine as described in claim 2 wherein said limit switch comprises a pair of contact springs connected to the current supply for the return device and the magnetic clutch 4i. A dictating machine as described in claim 3 wherein said contact springs are actuated by the sound head carriage through said linkage.

5. A dictating machine as described in claim 4 wherein said linkage comprises a pawl adapted to be rotated and displaced perpendicular to the axis of said cylinder, one end of said pawl being adapted to actuate said pair of contact springs and carrying thereon the return element.

6. A dictating machine as described in claim 5 wherein said retu m element is a nose having an edge extending in the feeding direction of the sound head carriage to engage an edge of the sound head carriage when it is returned.

' 7. A dictating machine as described in claim 6 wherein said edge of the sound head carriage is an edge defining an opening provided in a sidewall of said sound head carriage facing the.

limit switch and wherein said nose extends into said opening when said sound head carriage is returned.

8. A dictating machine according to claim 7 wherein the 1 other end of said pawl is proximate to said cam and has a carrier hook adapted to be engaged by said cam.

9. A dictating machine as described in claim 8 wherein said pawl is held by a return spring in arest position and wherein the displacement of the pawl is effected in two successive phases by said return cam when it,; rotates, said first phase being effected by means to displace the-pawl perpendicularly to the cylinder shaft until said nose is disengaged from said opening and the sound head carriage is positioned in its starting position and said second phase being effected by means to turn the pawl until the carrier hook is disengaged from the return cam, whereby after said displacement the pawl is returned by the return spring into its; rest position and the limit switch 15 deactivated causingthe cylinder drive to stop and the the front end and a stop at.the rearend of a cylinder, a return device for automatically returning the sound head carriage and a control circuit-operationally connected to said machine for setting the operating states of the machine, the improvement comprising a limit switch to disconnect the device from the sound head carriage and to connect h the magnetic clutch for the cylinder drive, said switchbeing arranged at the end of the return path of the sound head carriage and adapted to be actuated by the sound head carriage when it is returned and means to return said sound head carriage to a starting position and to deactivate said limit switch after it has been activated, said means including a return element arranged at the end of the return path which acts on the soundhead carriage and which can be displaced by a return cam fixed to rotate with said cylinder, said return element being operationally connected with said return camby a linkage having an end adjacent to said cam, said end adapted to be displaced by the returning sound head carriage into the path of motion of said cam, said sound head carriage adapted to be moved into a starting position by said cam through said linkage when said cylinder rotates and said end is contacted by said return cam, said cylinder adapted to be set in a starting position determined by the deactivation of said limit switch when said sound head carriage is moved. 

1. A dictating machine comprising, in combination, a cylinder driven in a feeding direction through a clutch, a sound head carriage with a sound head for recording and reproducing sound, said sound head carriage being adapted to move along a path parallel to the axis of said cylinder, a limit switch to engage said clutch with said cylinder, said switch being positioned adjacent to one end of said cylinder in the return path of movement of said sound head carriage and adapted to be actuated by said sound head carriage, means to place said sound head carriage in a starting position and to deactuate said limit switch after it has been actuated, said means including a return element arranged adjacent said one end of said cylinder and adapted to displace said sound head carriage and to be displaced by a return cam fixed to rotate with said cylinder, a linkage extending from said return element and having one end adapted to be disposed in the path of movement of said rotating return cam, said cam being adapted to contact said linkage whereby when said cam contacts said linkage said return element is moved, thusly displacing said sound head carriage to said starting position and deactuating said limit switch to set said cylinder in a starting rotary position.
 2. A dictating machine as described in claim 1 having a return device operatively associated with said carriage for automatically returning said sound head carriage to one end of said cylinder, a control circuit connected to said machine for setting the operating states of the machine and wherein said limit switch is used to deactivate said return device.
 3. A dictating machine as described in claim 2 wherein said limit switch comprises a pair of contact springs connected to the current supply for the return device and the magnetic clutch.
 4. A dictating machine as described in claim 3 wherein said contact springs are actuated by the sound head carriage through said linkage.
 5. A dictating machine as described in claim 4 wherein said linkage comprises a pawl adapted to be rotated and displaced perpendicular to the axis of said cylinder, one end of said pawl being adapted to actuate said pair of contact springs and carrying thereon the return element.
 6. A dictating machine as described in claim 5 wherein said return element is a nose having an edge extending in the feeding direction of the sound head carriage to engage an edge of the sound head carriage when it is returned.
 7. A dictating machine as described in claim 6 wherein said edge of the sound head carriage is an edge defining an opening provided in a sidewall of said sound head carriage facing the limit switch and wherein said nose extends into said opening when said sound head carriage is returned.
 8. A dictating machine according to claim 7 wherein the other end of said pawl is proximate to said cam and has a carrier hook adapted to be engaged by said cam.
 9. A dictating machine as described in claim 8 wherein said pawl is held by a return spring in a rest position and wherein the displacement of the pawl is effected in two successive phases by said return cam when it rotates, said first phase being effected by means to displace the pawl perpendicularly to the cylinder shaft until said nose is disengaged from said opening and the sound head carriage is positioned in its starting position and said second phase being effected by means to turn the pawl until the carrier hook is disengaged from the return cam, whereby after said displacement the pawl is returned by the return spring into its rest position and the limit switch is deactivated causing the cylinder drive to stop and the starting position of the cylinder to be determined.
 10. A dictating machine as described in claim 9 wherein said pawl has an oblong slot and is secured on a supporting part having a journal, said journal passing through said slot and wherein the journal slides along edges of the slot during the displacement of the pawl.
 11. In a dictating machine having a cylinder driven in a feeding direction through a magnetic clutch, a sound head carriage for recording and reproducing sound guided parallel to the cylinder and moved back and forth between a stop at the front end and a stop at the rear end of a cylinder, a return device for automatically returning the sound head carriage and a control circuit operationally connected to said machine for setting the operating states of the machine, the improvement comprising a limit switch to disconnect the device from the sound head carriage and to connect h the magnetic clutch for the cylinder drive, said switch being arranged at the end of the return path of the sound head carriage and adapted to be actuated by the sound head carriage when it is returned and means to return said sound head carriage to a starting position and to deactivate said limit switch after it has been activated, said means including a return element arranged at the end of the return path which acts on the soundhead carriage and which can be displaced by a return cam fixed to rotate with said cylinder, said return element being operationally connected with said return cam by a linkage having an end adjacent to said cam, said end adapted to be displaced by the returning sound head carriage into the path of motion of said cam, said sound head carriage adapted to be moved into a starting position by said cam through said linkage when said cylinder rotates and said end is contacted by said return cam, said cylinder adapted to be set in a starting position determined by the deactivation of said limit switch when said sound head carriage is moved. 